Materials Science Forum Vols. 539-543

Abstract: In this paper, we present an analytic approach for the prediction of roll force to be applicable to the billet rolling process which consists of a series of horizontal stands and vertical stands. The approach is based on the deformation shape and employs the assumption that the deformation homogeneously occurs in three directions. Strain and strain rate are calculated by the geometric relationships between those components and the prescribed deformation functions. By integrating the stress components along the rolling direction, roll force is finally obtained. The prediction accuracy of the proposed model is examined through comparison experimentally mesured roll force with computed ones.

Abstract: Nickel-base alloys are mostly used for high-temperature applications, many of which are heavily loaded safety components. The material properties highly depend on the microstructure, which, in turn, depends on the metal forming process and the heat treatment. FEM integrated microstructure models can satisfactorily describe the grain size development due to dynamic and static recrystallisation during a metal forming processes and the heat treatment. The simulation results obtained from modeled compression experiments are very promising so that consequently, simulations of more sophisticated processes, like multi-pass open die forging or radial forging, is the next reasonable goal. However, the computation times for the simulation of these processes are still unsatisfactorily long and thus, their application is deterred. To accelerate the simulations, a multi-mesh algorithm was implemented to the Finite-Element simulation package PEP & LARSTRAN/SHAPE. This method uses a Finite-Element mesh that is fine in the deformation zone and coarse in the remaining areas of the workpiece. Due to the movement of the tools during the simulation, the deformation zone moves across the workpiece and thus, necessitates a remeshing with a transition of the finely meshed area. A second mesh, which is fine over the entire volume of the workpiece, is used to store the nodal data and simulation results, which get transferred to the simulation mesh every time a remeshing operation becomes necessary. In combination with an adopted data transfer algorithm, this second mesh is used to minimize the loss of accuracy, if a previously finely meshed area becomes a coarsely meshed area. This simulation model can be used to optimize forging process chains with respect to grain size distribution as well as cost effectiveness and energy consumption.

Abstract: The current article presented appropriate models using a new parameter recently introduced by the authors to accurately predict the atomic transport coefficients, i.e. viscosity and self-diffusivity, of liquid metallic elements at their melting points. The models for both the meltingpoint viscosity and self-diffusivity are expressed in terms of well-known physical quantities; atomic mass, atomic volume, melting point, melting-point surface tension, and the new parameter T ξ . Moreover, the authors derived expressions for the temperature dependence of the atomic transport coefficients of liquid metallic elements in terms of melting point temperature. These two models give very good agreement with experimental data for various metallic liquids. Using the models, self-diffusivities were predicted for liquid aluminum, calcium, and magnesium.

Abstract: According as the demand of miniature metal balls of various diameter increases, processing property and a variety of coverage are important. In this study, especially an optimal groove design of cutting roller was investigated for determining size and shape of metal ball in the manufacturing system. The effects of radius of the groove and radius of the knife-edge of cutting roller and the speed of roller as process parameters were calculated and analyzed. We applied data of rigid-plastic FEM Simulation with DEFORM3D and ANSYS in basic design of equipment to solve these issues, and checked processing parameter about metal balls manufacturing process that use cutting process of metal wire stock in this research. This paper deals with the new improved process of producing miniature STS316L steel balls continuously. Our first goal is to develop a much more efficient equipment and a much more economical production process

Abstract: The methods of sensitivity analysis allow to estimate the influence of parameters determining the geometrical, physical, boundary and initial conditions on the course of thermal processes in the system considered. In this paper the possibilities of shape sensitivity analysis application (SSA) in the thermal theory of foundry processes are discussed. In particular, the direct approach is presented because it seems that for practical applications this variant of sensitivity analysis is more effective. The theoretical base of SSA is presented in chapters 1 and 2, next the practical aspects of the method are discussed. In the final part of the paper the examples of computations can be found.

Abstract: Alongside volume fraction, VV, and area per unit of volume, SV, the integral interface curvature per unit of volume, MV, or the average interface curvature, H, are important microstructural descriptors. For grain growth, the grain boundary curvature is of special importance because, in addition to its geometrical significance, it is also the driving force for boundary migration. Notwithstanding its importance, curvature has been seldom measured and utilized in the analysis of polycrystals. Geometrical models were derived for the average curvature of individual grains, of grain boundaries and of grain edges, as a function of the mean intercept length. These models show good agreement with curvature measurements in an Al-1mass%Mn alloy. Furthermore, this work shows how grain boundary curvature measurement can be applied to normal grain growth as well as to the effect of particles on grain boundary pinning.

Abstract: Reinforcement bars are chiefly used in the building industry at production of reinforced concrete constructions and as working elements in bridge building. An important factor for strength joining bar and concrete are dimensions and positioning of ribs at the bar’s surface. In this paper the computer simulation of the rolling of the round reinforcement bar is presented. It has been performed in order to define the specific features of the mode of metal flow in the roll gap and to determine the effect of the shape and dimensions of the roll on the pitch of the ribs of the finished bar.

Abstract: First numerical results for microstretch continua, embedded in a hierarchy of generalized continuum models,will be presented. The governing equations are derived using a variational approach, providing an alternative to Eringens approach of modeling microstretch continua. A constitutive theory for linear elastic microstretch continua is formulated and used in the simulations. Simple examples will be investigated in order to demonstrate the compatibility of the model hierarchy. The results obtained so far are promising and suggest that a further in-depth analysis of (in)elastic microstretch continua based on the here proposed consistent and computationally simple approach to microstructured materials is worthwile.

Abstract: A continuum model for composite materials made of short, stiff and tough fibres embedded in a more deformable matrix with distributed microflaws is proposed. Based on the kinematics of a lattice system made of fibres, perceived as rigid inclusions, and of microflaws, represented by slit microcracks, the stress-strain relations of an equivalent multifield continuum is obtained. These relations account for the shape and the orientation of the internal phases and include internal scale parameters, which allow taking into account size effects. Some numerical analyses effected on a sample fibre-reinforced composite pointed out the influence of the size and orientation of the fibres on the gross behaviour of the material.